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GLF4, Abuja Nigeria, 2018
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|On 12 September 2018, a Gulfstream G-IV overran the runway at Abuja after the air/ground status system failed to transition to ground on touchdown and the crew were slow to recognise that as a result neither spoilers nor thrust reversers had deployed. In the absence of recorded flight data, it was not possible to establish why the air/ground sensing system did not transition normally but no fault was found. The aircraft operator’s procedures in the event of such circumstances were found to be inadequate and regulatory oversight of the operator to have been comprehensively deficient over an extended period.|
|Actual or Potential
|Human Factors, Runway Excursion|
|Aircraft||GULFSTREAM AEROSPACE Gulfstream 4|
|Type of Flight||Public Transport (Non Revenue)|
|Origin||Murtala Muhammed International Airport|
|Intended Destination||Nnamdi Azikiwe International Airport|
|Take off Commenced||Yes|
|Location - Airport|
|Airport||Nnamdi Azikiwe International Airport|
|Tag(s)||Inadequate Airworthiness Procedures,|
Inadequate Aircraft Operator Procedures,
Ineffective Regulatory Oversight,
Root Cause Not Determined,
Copilot less than 500 hours on Type,
PIC aged 60 or over
|Tag(s)||Inappropriate crew response (technical fault),|
Procedural non compliance,
Ineffective Monitoring - PIC as PF
|Tag(s)||Overrun on Landing,|
Ineffective Use of Retardation Methods
|Damage or injury||Yes|
|Causal Factor Group(s)|
On 12 September 2018, a Gulfstream G-IV (5N-BOD) being operated by SkyBird Air on a non-revenue domestic positioning flight from Lagos to Abuja overran the 3610 metre-long runway 22 at destination after touchdown following an ILS approach in night VMC and finally stopped in mud approximately 70 metres beyond its end. None of the six occupants were injured but two approach lights were impact-damaged by the aircraft landing gear and aircraft right hand flap was damaged by debris impact during the overrun.
An Accident Investigation was carried out by the Nigerian Accident Investigation Bureau (AIB) but its scope was hampered by the discovery following recovery of both the SSFDR and the CVR from the aircraft that the former had not recorded any relevant data for over 2 years and that the latter had also not been recording any data for a prolonged period previously.
The last flight correctly recorded by the SSFDR was found to been a flight to the USA in June 2016 for a Certificate of Airworthiness Renewal Inspection during which deficiencies were found. In August 2017 when the Nigerian CAA requested the required FDR readout and sensor analysis for the aircraft, it was not submitted and an alleviation from this requirement was subsequently requested and granted until the next C of A renewal which was due two weeks after the accident occurred. When download of the CVR was attempted, it was found that it was inoperative because the bulk erase coil had melted, probably during an attempt to accomplish a bulk erase and possibly because it was faulty.
The 61-year-old Captain, a Nigerian national who was PF for the accident flight, had a total of 8,436 hours flying experience of which 1,418 hours were on type. The 31 year-old First Officer, a Namibian national, had a total of 4,607 hours flying experience of which 42 hours were on type.
It was established that the accident flight had been the second of two flights the crew had operated that day, the first being a charter flight from Abuja to Lagos. The return flight was provided with radar vectors to an ILS 22 approach during which the A/T was reported to have been disengaged at approximately 500 feet aal and the AP at approximately 200 feet aal. The flight crew reported having tested the air ground proximity system, armed the ground spoilers and completed the applicable checklists. The VREF used was reported to have been 140 KIAS. After touchdown, which the Captain and the TWR Controller both stated had been made “within the first third of the runway”, it was stated that reverse thrust was selected normally but the rate of deceleration was considered to have been “slower than expected” and "neither the ground spoilers and thrust reversers had deployed”. The crew response to this situation appeared to have been slow and as the end of the runway was approached, the Captain called “no spoilers” and then manually deployed them as well as (successfully this time) the thrust reversers whilst continuing to brake. The aircraft remained on the runway extended centreline as it exited the end of the runway onto grass and eventually came to a stop in mud. The reported wind around the time of the landing was light and variable and the un-grooved runway surface was wet. The Captain subsequently stated that the touchdown had not been the firm one which he had intended given the wet, un-grooved surface.
In the absence of any findings which would explain the initial failure of the air/ground status system to transition to ground, it was observed by the Investigation that a delay in thrust reverser deployment would have occurred if the thrust levers had not been placed in the fully-aft (idle) position. It was suggested that “having realised that the thrust reversers and the ground spoilers would not deploy, the crew might have (then) closed the throttle to idle detent”. This corrective action appeared to have been unduly delayed with inevitable consequences despite the long runway.
The Investigation did not find any documented SOP in the Flight Operations Manual ( FOM) which required either pilot to call out correct automatic spoiler deployment or any failure to deploy. It merely stated that if automatic deployment did not occur, the Captain was then responsible for their manual extension regardless of which pilot was PF.
Some significant irregularities in relation to the operational control of the accident aircraft’s flights were found. In order for the aircraft to be used for commercial charter operations, its owner had signed an Aircraft Management Agreement (AMA) with AOC holder SkyBird Air under which the owner paid for aircrew, fuel and aircraft maintenance whilst SkyBird Air made its call sign available for such operations. However, it was found that the Nigerian CAA as regulator had issued Ops Specs in relation to SkyBird Air’s AOC which assigned Operational Control of the aircraft’s commercial flights to the aircraft owner so that applicable regulatory requirements were not satisfied. Quite separately, a number of irregularities were also found in the 2017 renewal of SkyBird Air’s AOC by the Nigerian CAA.
Although the accident flight was made for non-revenue positioning purposes, the same aircrew had operated the aircraft’s previous revenue sector from Abuja to Nigeria. The Investigation found irregularities with the Senior Cabin Crew Member’s (SCCM) authority to work on both flights - they were not type rated on G-IV and despite being neither trained nor otherwise authorised to act as a Cabin Crew Instructor, they were training another member of the operator’s cabin crew who was also not aircraft type rated.
The Cause of the runway overrun was formally documented as “the delayed response of the crew in recognising that the ground spoilers and thrust reversers were locked out”.
A Contributory Factor was also identified as “the delayed deployment of ground spoilers which led to the flight crew’s problems in stopping the aircraft within the remaining available runway length”.
Nine Safety Recommendations were made as a result of the Investigation as follows:
- that the Federal Airports Authority of Nigeria (FAAN) should ensure that disabled aircraft are promptly removed from the incident site in accordance with Disabled Aircraft Recovery Manual for Abuja (Chapter 3 removal instructions). [2020-004]
- that the Federal Airports Authority of Nigeria (FAAN) should ensure the roles and responsibilities of stakeholders as stipulated in the Airport Emergency Plan (AEP) are strictly adhered to in case of any occurrence. [2020-005]
- that the Federal Airports Authority of Nigeria (FAAN) should ensure that airport RFFS units are adequately staffed at a level that enables their personnel, upon arrival at an accident scene, to conduct exterior fire-fighting activities, interior fire suppression attack and a rescue mission concurrently. [2020-006]
- that the Nigerian Civil Aviation Authority (CAAN) should ensure that all G-IV operators adhere strictly to normal operating procedures regarding the air/ground sensing system. [2020-007]
- that the Nigerian Civil Aviation Authority (CAAN) should ensure that all G-IV operators, require flight crew to call-out if the ground spoilers do not automatically deploy and the thrust reversers are not deployed during landing, also a call-out when the ground spoilers have deployed and verify they include these procedures in their checklists, and training programs. The procedures should clearly identify which pilot is responsible for making these call-outs and which pilot is responsible for deploying the spoilers if they do not automatically deploy. [2020-008]
- that the Nigerian Civil Aviation Authority (CAAN) should intensify its oversight of SkyBird Air’s operations. [2020-009]
- that the Nigerian Civil Aviation Authority (CAAN) should comply with the AOC application/renewal process and ensure that the process is completed in accordance with the guidance materials issued by the Authority prior to issuance of the AOC to applicants. [2020-010]
- that SkyBird Air should ensure that all their cabin crew are adequately and properly type rated on the specific aircraft to be flown by a cabin crew member in accordance with the Operations Manual. [2020-011]
- that SkyBird Air should should ensure that all flight release documents are duly signed by the commander of the flight before departure and appropriate copies are kept on board the aircraft. [2020-012]
The Final Report of the Investigation was released on 26 November 2020.